Dec. 1, 1865.] 



SCIENCE-GOSSIP. 



267 



Last, not least, Dr. Johk Lindley, who had 

 scarcely left his cradle when Sir William Hooker's 

 botanical career commenced, only survived him a 

 fev/ weeks. He also was born in Norfolk, a county 

 famous for the production of excellent botanists, 

 in the year 1799. At the age of twenty he pub- 

 lished a translation of a French work on fruit, and 

 the next year appeared his first original production, 

 a Monograph of Roses. He assisted Loudon with 

 his "Encyclopaedia of Plants;" produced a great 

 monument for himself in his " A''egetable Kingdom ; " 

 was for a quarter of a centiu:y Professor of Botany 

 at University College ; wrote the majority of the 

 botanical articles for the " Penny Cyclopaedia;" and 

 was for many years associated with the Botanical 

 Register and the Gardener's Chronicle. Besides this 

 he was doubtless our best special authority for- 

 orchidaceous plants. 



It is impossible to estimate the influence of these 

 two men on botanical science in this country during 

 half a century. If we endeavour to compare what 

 it was under the old Linnsean system, when they 

 each began the study of plants, with what it is when 

 both have but just departed, we shall be astonished 

 at the changes, in which each performed his share 

 of the work. 



It vrill be long ere the eventful year now fast 

 drawing to a close wiU be forgotten. This year, 

 which deprived America of its President and Britain 

 of its Premier ; Ptussia of its Czarevitch and Borne 

 of its Anglican Cardinal, will be remembered 

 throiigli many generations. But to men of science 

 in England it will be remembered as the year which 

 robbed them of some of their noblest veterans ; to 

 botanists especially as that in which Hooker and 

 Lindley died. "Peace to the souls of the heroes 

 departed." They have left us for a land where, not 

 only " the wicked," but the minor cares and anxieties 

 of this life — 



. . . cease from troubling, 

 And the weary are at rest. 



WHAT TO SEEK AND WHAT TO AVOID 

 IN THE CHOICE OE A MICROSCOPE. 



N these days, when the IMicroscope is becoming 

 a valuable auxiliary in the education of the 

 people, a few brief hints on the selection of an 

 instrument by whose aid we pry into Natui'e's 

 minutiae, may not be considered out of place in the 

 pages of SciEKCE Gossip. 



As the stability of a house depends on the solidity 

 of its foundations, so does that of a microscope 

 depend on similar qualities— the solidity and 

 strength of its stand. The tripod, or three-footed 

 stand, seems of all formsto be that most generally 

 adopted by our best makers, and from which we 

 may fairly conclude that it has recommended itself 

 to their notice by its firmness and freedom from 



tremor. The feet of a tripod should be both 

 broad and solid, so as to furnish a firm support 

 or base to the pillars or cheeks resting thereon, 

 and between which the whole optical part of the 

 instrument, witli its lenses, stage, substage, and 

 illuminating apparatus, is suspended. And these 

 portions of a microscope should be so weU balanced, 

 that the centre of gravity will ' not be materially 

 disturbed, at whatever angle its optical part may be 

 inclined. In a badly-constructed microscope there 

 is often a tendency to tip over in some given direction 

 whenever the body is inclined from a vertical to a 

 horizontal position. And it is just as well to test 

 this tendency before purchasing an instrument. 

 In microscopes constructed with a single pillar rest- 

 ing on the centre of a round foot, this tendency is 

 augmented, and such an instrument should be re- 

 jected as unstable. In working with the microscope, 

 it is frequently necessary to incline the body of the 

 instrument for convenience of observation. To 

 allow of such a motion, the optical portion must be 

 attached to its pillars or supports by hinge or 

 cradle joints, wliich enable the body to be incHued 

 ninety degrees from the perpendicular. These 

 should work with just sufficient stiifness to retain 

 the body of the microscope at whatever angle it may 

 be placed. Where, however, the microscope is in 

 daily use, the wear and tear will tend to loosen the 

 joints ; but the fault may be easily remedied by 

 simply tightening the screws. In the majority of 

 instruments the tube or body is firmly screwed into 

 one end of an arm, while the other end is attached 

 to a triangular bar, with a rack cut on one of its 

 edges, in which works a pinion with two large milled 

 heads. In the more modern instruments, the 

 triangular is superseded by a square form of bar, 

 having the rack-work on one of its sides. But I 

 am not aware whether or not greater steadiness 

 and smoothness of motion is gained by this mode 

 of construction. Some makers prefer a stand in 

 which the body of the microscope is supported 

 along the greater portion of its length. In such a 

 form the rack-work is attached to the body itself, and 

 has two small flanges that work in grooves, ploughed 

 out of the limb. By this contrivance the body is 

 kept in contact with the arm that supports it, and 

 on which it freely moves. This plan possesses 

 the merits of simplicity and steadiness, but does 

 not, as in the former plan, admit of the body being 

 turned away from the stage, an advantage which is 

 sometimes of use to the microscopist. Whatever, 

 however, may be the mode of supporting the body, 

 the rack and pinion should be accurately cut to fit 

 each other ; unless great nicety is here shown, we 

 shall fail to obtain that smooth and even motion so 

 necessary to securing the focus of a sensitive object- 

 glass. A badly-cut rack may be known by its 

 jerking uneven motion, which communicates a most 

 disagreeable vibration to the whole instrument, and 



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